Fluid-pressure control of turbo ventilation



March 30 1926.

R. E. GHMMAN ET AL FLUID PRESSURE CONTROL OF TURBG VENTILATION Original Filed July 20, 1925 k m w a I WITNESSES Patented Mar. 30, 1926. MM

UNITED s'raru are-.. CQPY was PATENT mesa RALPH IE. GILMAN, OF PITTSBURGH, DONALD BRATT, OF IRWIN, AND CARL J. FECH- HEIMER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNORS TO "WESTINGHOUSE ELEC- TRIO 8: MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

FLUID- PRESSURE CONTROL OF TURBO VENTILATION.

Application filed. July 20, 1923, Serial No. 652,670. Renewed December 1, 1925.

T 0 all whom it may concern:

Be it known that we, RALPH E. GILMAN, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, DONALD BRATT, a subject of the King of Sweden, and a resident of Irwin, in the county of estmoreland and State of Pennsylvania, and CARL J. Fncnnmrrnn, a citizen of the United States, and a resident of Pittsbur h, in the county of Allegheny and State or Pennsylvania, have invented a new and useful 1H1".

provement in Fluid-Pressure Controls of Turbo Ventilation, of which the following is a specification.

Our invention relates to the ventilation of dynamo-electric machines and it has particular relation to turbo-alternators and other machines having relatively great length, wherein the ventilation is secured by means of air flowing radially through radial ducts in the stator member and flowing axially through the air-gap.

The principal object of our invention is to provide a new system of ventilation of the general type just mentioned, wherein the air intake pressure at the ends of the air-gap is adjusted to the proper proportion of the air intake pressure applied to the intake chamber surrounding the stator member in order to soon e maximum uniformity of the radial air velocities in all of the radial ducts of the stator member.

With the foregoing and other objects in view, our invention resides in the combinations and arrangements hereinafter de scribed and claimed, and illustrated in the drawing, wherein:

Figure 1 is a cent a], longitudinal view of a dynamo-electric machine embodying our invention.

Fig. 2 is a similar view of a modification, and

F ig. 3 is a curve diagram hereinafter referred to.

In Fig. 1 is shown an alternator comprising a stator member 9 and a rotor mem- )er 1O separated by an air-gap 11. The stator is provided with a magnetizable core 12 which comprises aplurality of bundles oi laminations 13, said bundles being sepa rated by radially-extending annular spaces or vents 1d. The stator core is wound with an altern'ating-current wind1ng, as indicated at 15.

with an enclosing end bell 16 which is provided with an. inlet opening 17 for receiving a ventilatingfiuid from any suitable source (not shown), as indicated by the arrows. Surrounding the magnetizable core member 12 are a. plurality of annular intake chambers 18 and a plurality of annular discharge chambers 19 and 20, the latter being provided with outlet openings 21, and the former being connected to the end-bell space by means of one or more tubular members 22.

A movable gate 2 1', which may be controlled by means of a handle 25, is provided in the end-bell space, preferably adjacent to the tubular member 22, whereby the dis-- tribution of the cooling fluid between the annular intake chambers 18 and the ends of the air-gap 11 may be controlled at. will.

Fig. 1 will be understood by reference to Fig. 3, showing the distribution of the radial velocities in the respectiveradial vents. It

has been found, as a result of a long series or" tests, that, when air is flowing axially through an air-gap or tube and discharging into radially disposed'vents distributed along the length of the tube, the radial velocities will tend to distribute themselves approximately in accordance with a sinewave curve, starting with a maximum at the balance point, or the point at which the axial velocity is zero, and falling off, toward the end o1 the tube, an amount depending upon the number of interposed radial vents. When the air pressure applied to the ends of the air-gap is too great, the distribution of the radial velocities in the entire machine is distorted, as indicated approximately by the dotted-line curves in 3, whereby extremely low radial velocities are obtained in the radial vents nearest the ends of the machine.

in accordance with our invention, the air The stator member is further provided pressures applied to the ends of the air-gap are reduced, not in ahit or miss fashion, as has been the only method known in the prior art, but in a scientific manner, which will be explained more in detail later on, with a view to obtaining approximately equal radial velocities in all of the :radial vents.

Machines'of the general class hereinbefore described, with the exception of the specific fluid-pressure controlling means, have long been known in the prior art, and it has long been recognized that the ventilation from the ends of the air-gap couldbe supplemented by additional means for passing a cooling fluid into the intermediate-parts of the'air ga'p through radial ventilating-ducts in the stator, as set forth in the Swiss Patent No. 37.;8l-3,'dated July 19., 1906.

While prior constructions of the general type just described have had, for their obje'c't, the prevention of overheating in "the centralportions of the machine, :the designs have all beendirected either to the problem of avoiding the necessity for utilizing the ventilating vair after it had become over heated in a long passage through the airgap to the central portions of tneinachine, or to the problem of securing a sufficient air flow without resort to excessive pressure heads on account of the insutlicientair-gap area in long machines.

According to our invention, the cooling is effected very largely by means of the radially flowing air, the axial flow being relied upon to a much lesser extent, and the quantity of air being such that its increase in temperature in the machine is relatively small. Animportant feature of our invention is that weaim to obtain uniformity of temperature conditions within the machine, by securing, as nearly as possible, uniform radial velocities in the radial ventilating spaces. If any variation should occur in the radial velocities, it is, of course, evident that somewhat lower velocities could be tolerated in the intake vents than in the discharge vents, on account of the necessarily lower temperature of the intake air.

The problem of calculating, in advance, the radial velocities which should be er:- pected in the radial vents is an exceedingly difficult matter, owing to the uncertainty as 'tothe'p-recise laws governing the air flow, and owing particularly to the lack of information on the effects of eddy currents and the losses of head which should be expected. Eaperimentation to determine the most advantageous arrangement has been practically impossible, heretofore, on accountof the very large size of the machines in which the 'present system of ventilation is utilizedand on account of the great cost of building experimental machines.

Asa result of an extensive investigation including a long series of experiments, we have determined a very simple relation between the air pressures at the end of the air-gap and in the intake chambers surrounding the stator, and the number of radial vents. It appears that we may write P, 1 +76 sin -e rifle-imp where P is the pressure in the end bell at theend of the air-gap, P. is the pressure in the stator intake chamber 18, 7c is a constant depending upon the shape of the intake at the end-bell end and apparently varying between the values-0.2 andOAt, and

S cross-sectional area of one radial vent at its most restricted portion, a cross-sectional area of the air-gap, L the number of radial vents in the intake group,

L the number of radial vents between the end of the machine and the balance point in the discharge group L L :the number of radial vents. between the balance point and the other end of the discharge group L (Fig. 3),

(I an intake tooth-drop constant determined largely by experience. and apparently varying between the limits 1.05 and 1.80 for different machines, and

G a discharge tooth-drop constant apparently made up of a constant ofthe order of magnitude of 0.6 .plus a con- The value of C usually lies between 0.60 and 1.20. The utility of the constants herein mein tioned is found chiefly in the facts that they hold for all pressure conditions encountered in ordinary practice and that they are con- S stant times stant not only for any given machine but.

also for machines of different sizes 0 -1? a given' type or pattern.

twill be understood that the regulating gate 2% will be manipulated to such a position that the ratio of pressures is substantially as given hereinabove, whereby .ap proximately equal conditions of maximum, minimum and mean radial velocities are obtained in each of the groups of the stator ventilating spaces.

In Fig. 2 is shown a slight modification wherein the air pressure is generated bv means of a fan 30 on the end of the rater member 10, the air supplied tothe end of the air-gap being reduced in pressure by means of a sleeve member 31 secured to the statormember and extending out over an extension 32 of the rotor member, in! order to provide a. restricted entrance area for the cooling fluid entering the ends of the airgap.

If desired, the sleeve 31 may be provided with one or more hinged segments 34 which may be operated b means of a handle to approach or recede from the rotor extension 32 in order to provide some adjustment of the air pressure admitted to the ends of the air-gap proper.

One or more of the end bundles of stator laminations are also cut away in order to provide abrupt increases in the air-gap area at the corresponding radial ventilating spaced in order to further increase the tiow or air radially in said ventilating spaces. The operation of the machine shown in Fig. 2 is otherwise similar to that already described in connection with Fig. 1.

While we have shown our invention in two preferred forms, it will be understood that various substitutions and modifications may be adopted by those skilled in the art without departing from the spirit of our invention, and we desire, therefore, that the appended claims be accorded the broadest interpretation consistent with the improvement over the prior art.

lVe claim as our invention:

1. A dynamo-electric machine having a retor and a stator wit-h an air-gap therebe tween, said stator embodying a ventilating system comprising a plurality of groups of radially extending ventilating spaces surrounding the air-gap, one or more groups of intake chambers surrounding one or more groups of radial spaces for conducting a cooling fluid radially inwardly, discharge means surrounding theremaining groups of radial s1 aces, entrance chambers for cooling fluid at the two ends of the air-gap, and tluidpressure means for maintaining such ditierent relative pressures in said intake chambers and said entrance chambers that all groups have substantially the same minimum radial velocities and the same maximum radial velocities of the cooling fluid.

2. A dynamo-electric machine having a retor and a. stator with an air-gap therebetween, said stator embodying a ventilating system comprising a plurality of groups of radially extending ventilating spaces surrounding the air-gap, one or more groups of intake chambers surrounding one or more groups of radial spaces for conducting a cooling fluid ,radially inwardly. discharge means surrounding the remaining groups or radial spaces, entrance chambers for cooling fluid at the two ends of the airap, and fluid-pressure means tor maintaining such ditl'erent relative pressures in said intake chambers and said entrance chambers that approximately equal average radial velocities are obtained in all of the groups.

3. A dynamoelectric machine having a rotor and a stator with an air-gap therebetween, said stator embodying a ventilating system comprisin a plurality of groups of radially extending ventilating spaces sur-' rounding the air-gap, one or more groups of intake chambers surrounding one or more groups of radial spaces for conducting a cooling fluid radially inwardly, discharge means surrounding the remaining groups of radial. spaces, entrance chambers for cooling fluid at the two ends of the air-gap, and fluid-pressure means for maintaining such different relative pressures in said intake chambers and said entrance chambers that approximately equal minimum radial velocities are obtained in all of the group. 4. A dynamo-electric machine having a rotor and a stator with an air-gap'therebetween, said stator embodying a ventilating system comprising a plurality of approximately equal groups of radially extending ventilating spaces surrounding the air-gap, one or more groups of intake chambers surrounding one or more groups of radial spaces other than the end groups for conducting a cooling fluid radially inwardly, discharge means surrounding the remaining groups of radial spaces, entrance chambers for cooling fluid at the two ends of the airgap, and fluid-pressure means for maintaining a lower pressure in said entrance chambers than in said intake chambers, the ratioot pressures being suchthat the balance points in the end discharge groups are approximately in the centers of said groups.

5. The combination with a dynamo-electric machine having a rotor and a stator having an air-gap thcrebetween, said stator having a plurality of radially extending ventilating passages surrounding said airgap, of means for supplying a cooling fluid to the peripheries of a plurality of radial passages and to the ends of the air-gap and for discharging said cooling fluid from the remaining radial passages, the intake radial passages being grouped in one or more sections and the discharge radial passages being grouped in a plurality of sections alternating with said intake groups, the pres sures and grouping being such that approximately equal conditions of maximum, mini mum and mean radial velocities are obtained in each of the groups of radial passages, in

accordance with the equation V P 1+lsin where P is the pressure at either end of the air-gap, P is the pressure at the peripheries of each of the stator intake radial passages, is a constant depending upon the shape of the intakes at the ends of the airgap and usually having a value between the limits 0.2 and Osl tor dril'erent machines, and

S being the minimum cross-sectional area of a radial passage, a being the cross-sectional area of the air-gap, L being the numberot radial passages in an intake group, L being the number of radial passages between either end of the air-gap and the balance point of the end group of discharge passages, L being the number of radial passages between said balance point and the other end of said discharge group, C being an intake tooth-drop constant determined by experiment for the particular machine and usually having a value between the limits 1.05 and 1.3 for diiterent machines, and Cd being a discharge tooth-drop constant determined by experiment for the particular machine and usually having a valuebetween. the limits 0.6 and 1.2 for different machines,

6. VA dynamo-electric machine having a rotor and a stator with an air-gap therebetween, said stator embodying a ventilating system comprising a plurality of radially extending ventilating spaces surrounding the air-gap, entrance chambers tor cooling fluid at the two ends of the air-gap, and means for maintaining fluidpressure in said entrance chambers, the stator member being cut away to abruptly increase the air-gap at one or more of the radial ventilating spaces near each end of the machine.

'7. A dynan'io-electric machine having a rotor and a stator with an air-gap therebetween, said stator embodying a ventilating system comprising, a plurality of groups of radially extending ventilating spaces surrounding the air-gap, one or more groups ofintake chambers surrounding one or more groups of radial spaces for conducting a cool ing fluid radially inwardly, discharge means surrounding the remaining groups of radial spaces, entrance chau'ibers for cooling fluid at the two ends 01'? the air-gap, and means for maintaining fluid pressure in said intake and entrance chambers, the stator member being cut away to abruptly increase the airgap at one or more of the radial ventilating spaces near each end of themachine.

8. A dynamo-electric machine having a rotor and a stator with an air-gap therebe tween, said stator comprising a magnetizable core member having a plurality of groups of ra dially extending ventilating spaces surrounding'thc air-gap, one or more groups cit-intake chamberssurrounding one or more groups ot radial spaces for conducting a cooling fluid radially inwardly, discharge means surrounding the remaining groups of radial spaces, an end bell enclosing a space at .each end of the machine, and communieating ducts from said end-bell spaces to said intake ichambers, the rotor having a portion extending beyond said stator core member, and the stator .having an annular member projecting out over said extending rotor portion for restricting the air-,gap entrance.

9. A dynamo-electric .machine having a rotor and a stator with .an air-gap the-rebetween, said stator comprising a magnetizable core member having .a plurality of I groups of radially extending ventilating spaces surrounding the air-gap, one or more groups oi rintake chambers surrounding one or more groups 0:6 radial spaces for conducting a cooling fluid radially inwardly, discharge means .surroundingthe remaining groups of radial spaces, an end bell enclosing a space at each end of the :machine, and communicating ducts from said .endbell spaces to said intake chambers, the rotor having a portion extending beyond said (stator core member, :and thestator having an annular member projecting out over said extending rotor portion for restricting the air-gap entrance, and the stator member being cut away to abruptly increase the air-gap at one or :more of the .radial ventilating spaces near each end of'the machine.

10. A dynamo-electric machine having a rotor and a stator with can air-gap t-herebetween, said stator-comprising a magnetizable core member :having a plurality of groups of radially extending ventilating spaces -surrounding the air-gap, one or more groups of intake chambers surrounding one or more groups of radial spaces for conducting a cooling .fluid radially inwardly, discharge means surrounding the remaining groups of radial spaces tor conducting a cooling fluid radially inwardly, discharge means surrounding the remaining groups of radial spaces, an'end bell enclosinga space at each end of the macliine, communicating ducts from said end-bell spaces to said intake chambers, and means for restricting the air gap at the ends thereof, the stator member being cut away to abruptly increase the airgap at one or more. of the radial ventilating spaces near each end of the machine.

In testimony whereof, we have hereunto Subscribed our names this 12th day of July, 1923.

RALPH E. GlLlllAN. DONALD BRATT. V CARL J. FE Cl-llll lllillt t. 

